Publication: Bioestratigrafía (graptolitos) del límite Ordovícico-Silúrico en los Pirineos orientales (curso alto del río Segre, Lleida)
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2017
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Sociedad Geológica de España
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Abstract
Se presenta una sección de pizarras negras graptolíticas donde, por vez primera en España, se registra de manera continua el límite Ordovícico-Silúrico. El perfil se localiza al este de Estana (Lleida), en la Zona Axial pirenaica. El límite se localiza 2,20. m por encima del techo de la Cuarcita de Bar, cuya edad ordovícica queda aquí demostrada. Las asociaciones de graptolitos del Hirnantiense superior pertenecen a la Biozona de Metabolograptus persculptus y a la llamada “fauna pre-ascensus”, en tanto que los graptolitos del Silúrico basal corresponden a la Biozona de Akidograptus ascensus. El descubrimiento de esta sección es bastante excepcional en las plataformas del sur de Gondwana, donde los graptolitos post-glaciares son extremadamente raros. Entre las formas silúricas, se presenta el tercer hallazgo mundial de la especie Rickardsograptus? bifurcus, definida en China y reconocida también en los Alpes Cárnicos de Austria.
A unique graptolitic black-shale section ranging across the Ordovician-Silurian boundary interval has been found in the Pyrenees (NW Spain), at Riu de Quer locality, east of the town of Estana (province of Lleida). The Ordovician–Silurian boundary was identified 2.20 m above the top of the Bar Quartzite. Upper Hirnantian graptolites of the Metabolograptus persculptus Biozone and subsequent “pre-ascensus graptolite fauna” are common below the lowest occurrence of Akidograptus ascensus and associated taxa of the basal Silurian A. ascensus Biozone. The section is rather exceptional in Gondwanan Europe, where the post-glacial Hirnantian graptolites are extremely rare. Rickardsograptus? bifurcus recorded among the earliest Silurian taxa is an exotic element so far known only from China and the Carnic Alps of Austria.
A unique graptolitic black-shale section ranging across the Ordovician-Silurian boundary interval has been found in the Pyrenees (NW Spain), at Riu de Quer locality, east of the town of Estana (province of Lleida). The Ordovician–Silurian boundary was identified 2.20 m above the top of the Bar Quartzite. Upper Hirnantian graptolites of the Metabolograptus persculptus Biozone and subsequent “pre-ascensus graptolite fauna” are common below the lowest occurrence of Akidograptus ascensus and associated taxa of the basal Silurian A. ascensus Biozone. The section is rather exceptional in Gondwanan Europe, where the post-glacial Hirnantian graptolites are extremely rare. Rickardsograptus? bifurcus recorded among the earliest Silurian taxa is an exotic element so far known only from China and the Carnic Alps of Austria.